Merge pull request #1409 from dimagi/dv/api_versioning

Providing API version header from server to caller when available.

src/main/java/org/commcare/core/interfaces/HttpResponseProcessor.java

@@ -12,7 +12,7 @@ public interface HttpResponseProcessor {
     /**
      * Http response was in the 200s
      */
-    void processSuccess(int responseCode, InputStream responseData);
+    void processSuccess(int responseCode, InputStream responseData, String apiVersion);
 
     /**
      * Http response was in the 400s.

src/main/java/org/commcare/core/interfaces/ResponseStreamAccessor.java

@@ -5,4 +5,5 @@
 
 public interface ResponseStreamAccessor {
     InputStream getResponseStream() throws IOException;
+    String getApiVersion();
 }

src/main/java/org/commcare/core/network/ModernHttpRequester.java

@@ -33,7 +33,7 @@
  *
  * @author Phillip Mates ([email protected])
  */
-public class ModernHttpRequester implements ResponseStreamAccessor {
+public class ModernHttpRequester {
     /**
      * How long to wait when opening network connection in milliseconds
      */
@@ -87,7 +87,23 @@ public void makeRequestAndProcess() {
         }
         try {
             response = makeRequest();
-            processResponse(responseProcessor, response.code(), this);
+            final ModernHttpRequester requester = this;
+            processResponse(responseProcessor, response.code(), new ResponseStreamAccessor() {
+                /**
+                 * Only gets called if response processor is supplied
+                 * @return Input Stream from cache
+                 * @throws IOException if an io error happens while reading or writing to cache
+                 */
+                @Override
+                public InputStream getResponseStream() throws IOException {
+                    return requester.getResponseStream(response);
+                }
+
+                @Override
+                public String getApiVersion() {
+                    return requester.getApiVersion();
+                }
+            });
         } catch (IOException e) {
             e.printStackTrace();
             responseProcessor.handleIOException(e);
@@ -153,7 +169,8 @@ public static void processResponse(HttpResponseProcessor responseProcessor,
                     responseProcessor.handleIOException(e);
                     return;
                 }
-                responseProcessor.processSuccess(responseCode, responseStream);
+                String apiVersion = streamAccessor.getApiVersion();
+                responseProcessor.processSuccess(responseCode, responseStream, apiVersion);
             } finally {
                 StreamsUtil.closeStream(responseStream);
             }
@@ -181,14 +198,8 @@ public InputStream getResponseStream(Response<ResponseBody> response) throws IOE
         return cache.retrieveCache();
     }
 
-    /**
-     * Only gets called if response processor is supplied
-     * @return Input Stream from cache
-     * @throws IOException if an io error happens while reading or writing to cache
-     */
-    @Override
-    public InputStream getResponseStream() throws IOException {
-        return getResponseStream(response);
+    public String getApiVersion() {
+        return response != null ? response.headers().get("x-api-current-version") : null;
     }
 
     public static RequestBody getPostBody(Multimap<String, String> inputs) {